"With energy and vision, Paul Ryan has become an intellectual leader of the Republican Party,” Romney said. "He combines a profound sense of responsibility for what we owe the next generation with an unbounded optimism in America's future.”

He continued: “Paul and I are beginning on a journey that will take us to every corner of America. We’re offering a positive governing agenda that will lead to economic growth, to widespread and shared prosperity. ”

In an apparent nod to Ryan’s vulnerabilities on the issue, Romney pledged in a raised voice that his administration would give seniors no reason to fear for their entitlement programs.

“We will preserve and protect Medicare and Social Security and keep them there for future generations, ” Romney said.

In prepared remarks for the event, Ryan described himself and Romney as men who would lead the country to address “tough issues, ” using their complementary backgrounds in government and the private sector.

“Governor Romney is the man for this moment; and he and I share one commitment: we will restore the dreams and greatness of this country, ” Ryan said. “The commitment Mitt Romney and I make to you is this: We won’t duck the tough issues; we will lead. We won’t blame others; we will take responsibility. ”

(Also on POLITICO: Ryan speech: The Romney plan will save us)

From Norfolk, Romney embarks on a multi - day bus tour that takes him to North Carolina, Florida and Ohio, presumably with Ryan at his side. On a figurative level, Ryan will not leave Romney’s side for the rest of the campaign, and the debate over his credentials and ideas could transform how voters view the man at the top of the ticket.

Romney’s speech introducing Ryan was not yet over when the Obama campaign released a statement branding the lawmaker as a “radical” and an example of everything wrong with Congress, conservatism and the Republican Party.

“In naming Congressman Paul Ryan, Mitt Romney has chosen a leader of the House Republicans who shares his commitment to the flawed theory that new budget - busting tax cuts for the wealthy, while placing greater burdens on the middle class and seniors, will somehow deliver a stronger economy, ” Obama campaign manager Jim Messina said.

"The architect of the radical Republican House budget, Ryan, like Romney, proposed an additional $250,000 tax cut for millionaires, and deep cuts in education from Head Start to college aid. His plan also would end Medicare as we know it by turning it into a voucher system, shifting thousands of dollars in health care costs to seniors. As a member of Congress, Ryan rubber-stamped the reckless Bush economic policies that exploded our deficit and crashed our economy. Now the Romney-Ryan ticket would take us back by repeating the same, catastrophic mistakes.”